Energy absorber

ABSTRACT

An energy absorber wherein a tubular honeycomb member having a conically tapered end is collapsed by an anvil. The anvil has a concavity to accommodate the collapsed conically tapered end of the tubular honeycomb member and compresses the honeycomb energy absorbent member along a wave front which is substantially normal to the direction of honeycomb collapse.

' I United States Patent 1111 ,5

[72] Inventor Conrad R. Schudel [56] References Cited Danvflle, Calif- UNITED STATES PATENTS P 7985 3,010,540 11/1961 Dahlen 188/](C) {22] Filed Feb. 12, 1969 3,082,846 3/1963 Jensen et al. l88/l(C) [45] Paemd 3 130 819 4/1964 Marshall l88/l(C) [73] Assignee Hexcel Corporation Dublin, Calif. a corporation of California Primary Examiner-Duane A. Reger Attorney-Townsend and Townsend [$4] ENERGY ABSORBER ABSTRACT. An enelgy absorber wherein a tubular scmmssnrawing Figs honeycomb member having a conically tapered end is co]- [52] US. 188/1; lapsed by an anvil. The anvil has a concavity to accommodate 73/12 the collapsed conically tapered end of the tubular honeycomb [5|] Int- Fl6i' 7/12' member and compresses the honeycomb energy absorbent [50] Field of Search 73/ 1 1, 12; member along a wave front which is substantially normal to 188/lC the direction of honeycomb collapse.

I i i i I 1 A l PATENTED JAN 5 I97! PRIOR ART (PRIOR ART INVENTOR. CONRAD R. SCHUDEL ATTORNEYS a mpres d: e

ENERGY A 'soRBEri This inventionrelates to an energy absorbing honeycomb betweenthe columnar ends of honeycomb. cells; Generally, in

forming a honeycomb structure; a. plurality of corrugated ribbons of sheet material such as metal foil, paper, plastic or the like are bonded together at spaced node. points thereby fabricating a plurality of hollowmultisided columnarcells, all extending axially in the same-direction. Under 'the influence of mechanical forcesapplied to, the columnar ends of the cells, the cell wallsformed by the individual ribbons fold into. small accordionlike pleatsresulting in. alcompre'ssion' of the structure and absorption of energy.

Honeycomb is typically used. indestructible shock absor bers of the type wherein extraordinarily high forces. are dis= sipated. Such energy absorbers are found in bomb fin retarders, landing gear shock absorbers foraircraft, and the like, A. specific example of such, a structure can be found in US. Pat. No. 3,1 30,819 entitled Energy Absorber.

It is often desired to provide gradually. increasing energy. ab-. sorption. Honeycomb energy absorbingdevices. are known.

which have a wedge shaped endprovidinga gradually increas;

ingresistance as the collapse-of the honeycomb membercorn; mences, This increased resistance is impar'gt ed'because; the; compressing member or anvil. must o llapse; ever increasing cross sections of honeycombas it crushe's do wnwa dl er s -ben ficia dge 1 Anvils for. compressing wedge;shap have heretofore. comp honeycomb. before, the. anvil. in. greater; qu

taper of the, wedge is the longest. 'l hewwedgeshaped? honeycomb, gw hen compressed forms .angularlyg inclined wedgeshaped: configurationswhich have ma ifrontaqfi col gy absorber of the shaped end; v

Other objects, featuresand advantages of the present invention will be more apparent after referring to the following specification and attached drawings in which:

FIG. 1 is a side elevation view of a tubular honeycomb enerprior art before collapse at its conically FIG. 2 is a side elevation section of the energy absorber of FIG. 1 with its conicallyshaped 'end collapsed illustrating schematically the generation of splaying forces;

H6. 3 is a side elevation section of the energy absorber of this invention illustrating an anvil having a concavity for accommodating the collapsed conically shaped portion of the honeycomb;

FlC i. 4 is a side elevation section of the energy absorber of FIG; 3 illustrating the energy absorber with its 'conically shaped, portion collapsed interior of the conically apertured anvikand- FIG. -5' is a plan section illustrating a construction of the honeycom-bcore.

With reference to FIGS. 1 and 2', a honeycomb energy absorberof the prior art is'illustrated having an anvil A and a' tubular and. tapered honeycomb core C. Anvil A is. provided with a flat compressing surface 1 2 and is shown overlying and Contacting core'C' at the; apex" end of the conically tapered tube.

. As illustrated'iniFlGl 5;,core'C is circular in plan. Thiscore of'foil ,paper plastic, or the like: isformedifrom: aplurality. of

lapse inclined at an angle with respectto-thedirectionof,

honeycomb collapse. Thisinclinedwave frorithas been found to stress the honeycomb.ang ularly with respect tor, the axis;-

honeycornb collapse. The angular stressing causes delamina; tion of the bonded-node points and shearingofithematerial ofthe honeycomb, especially where the honeycpmb ispleatedon is being pleated. This in turn resultsintherupturebuckling v andoutward splaying of the cell-wall, thereby reducingthe number of aligned, effective energy absorbing cellsv and;

decreasingthe energyabsorption characteristics-.ofthematerie al. in this connection the bonded nodepointsof'most types of honeycomb are the structurallyweakest pointsofthe material;

and hence the nodepointswill usually fail. (bydelamination) before the ribbons themsclvBSWill collapsqshear, (mother-.

wisefail.

An object of this.invention"isto provide.anferrergytabsorbet? of the type having a tapered-honeycomb core. inewhichxthe honeycomb collapse does not generate;splaying or-delamina;v tion forces. Accordingly, the. compressing arivil is-contoured withre'spect to the compressed tapered=honeycomb;member; to provide awavefront of collapse normalto the direction'of honeycomb collapse, preventing the generationi ofiangular splaying force A further objectofl this inventionis to causej the collapsedg-j and corrugated .honeycomb material to lay. tip-upon ;.itself in -a.- wave front normal to theYdirection;of'honeycomh collapseto hich-further s form a uniformand adyancingwave.fro'ntrfromkw energy absorbing collapse can .occur. a

A featureand advantage of this inventionis thatthe superi--. or energy absorbing characteristics of a taperedrhoneycombmember are preserved, in an energy;absorber without the generation of delaminating forces.

during collapse.

With'referencetmlilG. 2, thecross-sectional crushedcon spirally multisid'ed. columnar-f cells .arerformed -exte'nding.

nally the ngthtoftlie-cylindr'icalcore c; i

videsazwedg'e shapedhoneycomb' core-'memberl6; This core membenexposesathe apexofethewedge shaped'crosssection of the ,core to anvil A. AnvilJA-when: it crushes the wedge shaped honeycomb, memberrl 6 meets increasing energyabsorbing-reprogressivelyincreasestin area.

figuration-of theyhoneycombisillustrated after com'plete col- 7 lapse; of-wedgegshaped.cross section' l6: Asrcawbe-seen; the

compressedwedge; shaped: cross section 16:: occupies. a

' reducedcross-,sectionv18havingwanizangularly inclined compressionwwave:fronts21: Wavefront-'21, .being inclinedz with. t respect-to-theaxis' of honeycombcollapseg exens-an'angularl'y inclined splayingforceF withrespecttothe-honeycomb core:

Two adverser conditionsare: created: in the honeycomb by" the configuration illustrated; in FIG. 22- First, the forces gcneratedby thecollapsingrwave-front are no longer'axial with the. cellsof thehoneycomb: Instead: these-forcesareincli'ned with respectztothe: honeycomb cells; wherethey: stress. the

bonded, nodes of 'the 1 honeycomb and; cause shearing: of "the honeycombwall eitherwhereithe-material has been-pleated or" alternately-iscollapsingand'being pleatedl- Secondly, the collapsedhoneycombrhas atendency to :slide'-angularly=alongatlie inclined-wave front oficollapsezfrom thetupwardslope-to the downwardislopenThis sliding ,tends-toshtear the pleatedwalls and. i prevent: the ;collapsed. honeycomb: core i from fonningrfa solid-;,base -;from[whichn further.;.uniforms honeycomlrcollapse I 16is shown-aunt" A's canrbeseen; the wedge shapedsection An additional feature and advantage of this invention is mar- 0 in a cylindrically shaped honeycomb' corefhaving-a,conically; tapered end compressed byaconically apertured anvil, forces; normal .to the axis of honeycomb collapse between :the wedge shaped honeycomb and anvil are precisely counterbalanced 25ibf'anviliAl. precisely accommodates=wedge 23 immediately.

above aeplane takenrnormal to-the-axis of 'honeycornb colv Cris" provided: at end" adjoining .anvilj X with a tapered: surface l4t'Surface 1-4 whenviewedin section pro- ,lapser 'lhis aligns the wave-front-of'honeycomb collapse 21" normallyto theaxisof lioneycomb collapse: All the -forces ex'-- erted from-thewave fronton'the collapsing core are 'parallelto the direction of honeycomb collapselschematically'illustrated *byarrovvsF'). As core C is progressivelycollapsed; wave front I 21 will continue to advance along the length of the core disposed substantially normal to the axis of honeycomb collapse.

As illustrated in FIG. 4, the honeycomb progressively collapses into small accordionlike pleats along its entire crushed portion. As one characteristic of honeycomb is that its compression or columnar strength exceeds by 50 percent its strength when partially crushed, the tapered conical construction assures that initial collapse commences at the wedge shaped portion of the cone 16. Since it is desirable to assure that collapse begins to occur uniformly at one portion of the honeycomb, anvil A will always first compress the tapered wedge shaped cross section 16 of the honeycomb and thereafter generate a wave front which moves progressively away from anvil A parallel to the direction of honeycomb collapse.

lt should be apparent that the wedged cross section 16 of the honeycomb core and anvil can be altered. This cross section can taper from the inner surface 30 of the core outwardly to the outer surface. Alternately, slope of the inclined portion of the wedge can be changed in configuration accordingly.

It will be noted that the inclined compressing surface of the honeycomb member 25 meets anvil A along an inclined interface 35. Normally during compression of the honeycomb, a sliding ofthe anvil with respect to the core would be expected.

In the tubular honeycomb core here shown, such sliding forces are precisely counteracted. As can be seen for each interface 35 tending to slide, there is presented an oppositely inclined interface 35' which interface exerts a sliding force between the anvil and core in an opposite and opposed direction. The interaction of these diametrically opposed sliding interfaces between the anvil and core mutually cancel one another and assist in the centering of anvil A as it moves along core C in its energy absorbing crush.

It is preferred that the columnar alignment of the honeycomb be disposed along the axis of honeycomb collapse. This enables the honeycomb to resist crush'along its axis of maximum strength where it maintains a highly uniform crush resistance.

The honeycomb energy absorber here shown has been tubular in configuration. While preferred, this is not necessary for the practice of this invention. Substantially any honeycomb core having a wedge-shaped cross section along planes parallel. to the axis of collapse will suffice. Moreover, the cross section configuration of the honeycomb cells is not critical. This invention applies equally well to honeycomb having a hexagonal cell cross section as well as the corrugated spiral wound cross-sectional construction here illustrated. The only requirement that the utilized honeycomb construction must meet is that the honeycomb be capable of an accordionlike and pleated collapse along the axis of its defined cellular structure.

I claim:

1. An article of manufacture comprising: a wedge shaped honeycomb core; an anvil; energy absorbing means for forcing said honeycomb core into said anvil at the apex of said wedge shape for collapsing said honeycomb to a compressed wedge shaped cross section; said anvil contoured to maintain the lower surface of said compressed wedge shaped cross section parallel to the direction of honeycomb collapse.

2. The invention of claim 1 and wherein: said honeycomb core is tubular and conically tapered at one end of said tube.

3. The invention of claim 2 and wherein said conically shaped honeycomb tube defines a cone of constant slope converging from the outside surface of said tube inwardly towards the inside surface of said tube.

4. The invention of claim 1 and wherein said anvil defines a concavity interior thereof.

5. An energy absorber haVing gradually increasing energy absorbing characteristics of the type wherein a wedge shaped honeycomb core is compressed under the influence of mechanical forces, said absorber comprising: a honeycomb core consisting of a plurality of columnated ribbons bonded to one another at space node points, said llbbOl'lS defining a multitude of hollow columnar cells; said core being wedge shaped in cross section; anvil means adapted to contact the point of said wedge shaped honeycomb core at one end and crush said honeycomb along the longitudinal axis of said hollow columnar cells; said anvil means sloped with respect to said wedge shaped cross section to dispose the wave front of honeycomb collapse substantially normal to the direction of honeycomb compression whereby forces exerted at said wave front are directed parallel to the direction of honeycomb collapse.

6. The invention of claim 5 and wherein said honeycomb core comprises spirally wound columnated ribbons of sheet material having bonded node points; and said core is provided with a conically tapered end.

7. An energy. absorber comprising: a honeycomb core having a decreasing cross-sectional area at one end thereof; an anvil corporatively contoured and engaging said honeycomb core at the decreased cross-sectional area for compression thereof; said anvil contoured with respect to said end of said core to direct the wave front of compression along said core normal to the direction of honeycomb collapse.

8. The invention of claim 7 and wherein said anvil is contoured for containing the compressed end of said honeycomb core immediately above a plane taken normal to the direction of honeycomb collapse. 

1. An article of manufacture comprising: a wedge shaped honeycomb core; an anvil; energy absorbing means for forcing said honeycomb core into said anvil at the apex of said wedge shape for collapsing said honeycomb to a compressed wedge shaped cross section; said anvil contoured to maintain the lower surface of said compressed wedge shaped cross section parallel to the direction of honeycomb collapse.
 2. The invention of claim 1 and wherein: said honeycomb core is tubular and conically tapered at one end of said tube.
 3. The invention of claim 2 and wherein said conically shaped honeycomb tube defines a cone of constant slope converging from the outside surface of said tube inwardly towards the inside surface of said tube.
 4. The invention of claim 1 and wherein said anvil defines a concavity interior thereof.
 5. An energy absorber haVing gradually increasing energy absorbing characteristics of the type wherein a wedge shaped honeycomb core is compressed under the influence of mechanical forces, said absorber comprising: a honeycomb core consisting of a plurality of columnated ribbons bonded to one another at space node points, said ribbons defining a multitude of hollow columnar cells; said core being wedge shaped in cross section; anvil means adapted to contact the point of said wedge shaped honeycomb core at one end and crush said honeycomb along the longitudinal axis of said hollow columnar cells; said anvil means sloped with respect to said wedge shaped cross section to dispose the wave front of honeycomb collapse substantially normal to the direction of honeycomb compression whereby forces exerted at said wave front are directed parallel to the direction of honeycomb collapse.
 6. The invention of claim 5 and wherein said honeycomb core comprises spirally wound columnated ribbons of sheet material having bonded node points; and said core is provided with a conically tapered end.
 7. An energy absorber comprising: a honeycomb core having a decreasing cross-sectional area at one end thereof; an anvil corporatively contoured and engaging said honeycomb core at the decreased cross-sectional area for compression thereof; said anvil contoured with respect to said end of said core to direct the wave front of compression along said core normal to the direction of honeycomb collapse.
 8. The invention of claim 7 and wherein said anvil is contoured for containing the compressed end of said honeycomb core immediately above a plane taken normal to the direction of honeycomb collapse. 